1561273501 has 4 divisors (see below), whose sum is σ = 1566198972. Its totient is φ = 1556348032.

The previous prime is 1561273471. The next prime is 1561273507. The reversal of 1561273501 is 1053721651.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 69305625 + 1491967876 = 8325^2 + 38626^2 .

It is a cyclic number.

It is not a de Polignac number, because 1561273501 - 2¹⁹ = 1560749213 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561273507) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2462260 + ... + 2462893.

It is an arithmetic number, because the mean of its divisors is an integer number (391549743).

Almost surely, 2^1561273501 is an apocalyptic number.

It is an amenable number.

1561273501 is a deficient number, since it is larger than the sum of its proper divisors (4925471).

1561273501 is an equidigital number, since it uses as much as digits as its factorization.

1561273501 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4925470.

The product of its (nonzero) digits is 6300, while the sum is 31.

The square root of 1561273501 is about 39512.9535848688. The cubic root of 1561273501 is about 1160.0935073750.

The spelling of 1561273501 in words is "one billion, five hundred sixty-one million, two hundred seventy-three thousand, five hundred one".